] Evolving Self-Diagnosing Hardware was first attempted by
] the author for some toy circuits in the hope it would be
] possible. The toy circuits attempted where a two bit
] multiplier and a one bit adder. After hundreds of
] thousands of generations, circuits evolved performing
] full diagnosis using about half the overhead the
] conventional solution would have required. For example
] when using two-input logic-gate technology, a two-bit
] multiplier can be implemented using 7 gates. Adding an
] extra copy, and 7 more gates for comparing 4 outputs, we
] have an overhead of 14 gates for the conventional voting
] system BIST solution. After four million generations the
] GA found a circuit (diagram) with the same behaviour
] using only 9 extra gates. It is hard to work out exactly
] what operating principles underlie its operation but it
] looks like it tends to use more XOR gates which always
] propagate a bit flip in one of their inputs, and also
] exploits design diversity to compare multiple sections of
] the circuit simultaneously.

I'm going to have to look at this in detail tonight.

I'm a little sceptical. Its not "hard to work out exactly what operating principles underlie" a 9 gate circuit. "Exploits design diversity" sounds like something a politician would say. I'm fairly certain that karnaugh maps produce solutions that are proveably optimised for simple cases like this. If he got results from this technique he probably started with an improperly designed circuit.

This is not to say that evolving hardware isn't interesting. It just seems like something isn't right with this example. A little math will tell me, and I'll post an update later.

Distributed Hardware Evolution